Some here have said it would be better to have a bunch of smaller publisher houses to adapt to the new technology. In this I do agree!

Large company's compared to small ones are slow to adopt change and are also shackled to their own inertia. It is proven the small company's are more nimble and can adapt to change quicker than any large organization.

Edit: To address the op original question, one of the reasons that publishing houses get so big is if they are publicly and not privately owned. The shareholders demand profit!

So that can and does cause growth by forcing the company to grow by buying out the little guys.